File Coverage

blib/lib/Capture/Tiny.pm

Criterion	Covered	Total	%
statement	227	246	92.2
branch	104	128	81.2
condition	53	75	70.6
subroutine	34	35	97.1
pod	8	8	100.0
total	426	492	86.5

use 5.006;
use strict;
use warnings;
package Capture::Tiny;
# ABSTRACT: Capture STDOUT and STDERR from Perl, XS or external programs
our $VERSION = '0.45'; # TRIAL
use Carp ();
use Exporter ();
use IO::Handle ();
use File::Spec ();
use File::Temp qw/tempfile tmpnam/;
use Scalar::Util qw/reftype blessed/;
# Get PerlIO or fake it
BEGIN {
  local $@;
  eval { require PerlIO; PerlIO->can('get_layers') }
    or *PerlIO::get_layers = sub { return () };
}

#--------------------------------------------------------------------------#
# create API subroutines and export them
# [do STDOUT flag, do STDERR flag, do merge flag, do tee flag]
#--------------------------------------------------------------------------#

my %api = (
  capture         => [1,1,0,0],
  capture_stdout  => [1,0,0,0],
  capture_stderr  => [0,1,0,0],
  capture_merged  => [1,1,1,0],
  tee             => [1,1,0,1],
  tee_stdout      => [1,0,0,1],
  tee_stderr      => [0,1,0,1],
  tee_merged      => [1,1,1,1],
);

for my $sub ( keys %api ) {
  my $args = join q{, }, @{$api{$sub}};
  eval "sub $sub(&;@) {unshift \@_, $args; goto \\&_capture_tee;}"; ## no critic
}

our @ISA = qw/Exporter/;
our @EXPORT_OK = keys %api;
our %EXPORT_TAGS = ( 'all' => \@EXPORT_OK );

#--------------------------------------------------------------------------#
# constants and fixtures
#--------------------------------------------------------------------------#

my $IS_WIN32 = $^O eq 'MSWin32';

##our $DEBUG = $ENV{PERL_CAPTURE_TINY_DEBUG};
##
##my $DEBUGFH;
##open $DEBUGFH, "> DEBUG" if $DEBUG;
##
##*_debug = $DEBUG ? sub(@) { print {$DEBUGFH} @_ } : sub(){0};

our $TIMEOUT = 30;

#--------------------------------------------------------------------------#
# command to tee output -- the argument is a filename that must
# be opened to signal that the process is ready to receive input.
# This is annoying, but seems to be the best that can be done
# as a simple, portable IPC technique
#--------------------------------------------------------------------------#
my @cmd = ($^X, '-C0', '-e', <<'HERE');
use Fcntl;
$SIG{HUP}=sub{exit};
if ( my $fn=shift ) {
    sysopen(my $fh, qq{$fn}, O_WRONLY|O_CREAT|O_EXCL) or die $!;
    print {$fh} $$;
    close $fh;
}
my $buf; while (sysread(STDIN, $buf, 2048)) {
    syswrite(STDOUT, $buf); syswrite(STDERR, $buf);
}
HERE

#--------------------------------------------------------------------------#
# filehandle manipulation
#--------------------------------------------------------------------------#

sub _relayer {
  my ($fh, $apply_layers) = @_;
  # _debug("# requested layers (@{$layers}) for @{[fileno $fh]}\n");

  # eliminate pseudo-layers
  binmode( $fh, ":raw" );
  # strip off real layers until only :unix is left
  while ( 1 < ( my $layers =()= PerlIO::get_layers( $fh, output => 1 ) ) ) {
      binmode( $fh, ":pop" );
  }
  # apply other layers
  my @to_apply = @$apply_layers;
  shift @to_apply; # eliminate initial :unix
  # _debug("# applying layers  (unix @to_apply) to @{[fileno $fh]}\n");
  binmode($fh, ":" . join(":",@to_apply));
}

sub _name {
  my $glob = shift;
  no strict 'refs'; ## no critic
  return *{$glob}{NAME};
}

sub _open {
  open $_[0], $_[1] or Carp::confess "Error from open(" . join(q{, }, @_) . "): $!";
  # _debug( "# open " . join( ", " , map { defined $_ ? _name($_) : 'undef' } @_ ) . " as " . fileno( $_[0] ) . "\n" );
}

sub _close {
  # _debug( "# closing " . ( defined $_[0] ? _name($_[0]) : 'undef' )  . " on " . fileno( $_[0] ) . "\n" );
  close $_[0] or Carp::confess "Error from close(" . join(q{, }, @_) . "): $!";
}

my %dup; # cache this so STDIN stays fd0
my %proxy_count;
sub _proxy_std {
  my %proxies;
  if ( ! defined fileno STDIN ) {
    $proxy_count{stdin}++;
    if (defined $dup{stdin}) {
      _open \*STDIN, "<&=" . fileno($dup{stdin});
      # _debug( "# restored proxy STDIN as " . (defined fileno STDIN ? fileno STDIN : 'undef' ) . "\n" );
    }
    else {
      _open \*STDIN, "<" . File::Spec->devnull;
      # _debug( "# proxied STDIN as " . (defined fileno STDIN ? fileno STDIN : 'undef' ) . "\n" );
      _open $dup{stdin} = IO::Handle->new, "<&=STDIN";
    }
    $proxies{stdin} = \*STDIN;
    binmode(STDIN, ':utf8') if $] >= 5.008; ## no critic
  }
  if ( ! defined fileno STDOUT ) {
    $proxy_count{stdout}++;
    if (defined $dup{stdout}) {
      _open \*STDOUT, ">&=" . fileno($dup{stdout});
      # _debug( "# restored proxy STDOUT as " . (defined fileno STDOUT ? fileno STDOUT : 'undef' ) . "\n" );
    }
    else {
      _open \*STDOUT, ">" . File::Spec->devnull;
       # _debug( "# proxied STDOUT as " . (defined fileno STDOUT ? fileno STDOUT : 'undef' ) . "\n" );
      _open $dup{stdout} = IO::Handle->new, ">&=STDOUT";
    }
    $proxies{stdout} = \*STDOUT;
    binmode(STDOUT, ':utf8') if $] >= 5.008; ## no critic
  }
  if ( ! defined fileno STDERR ) {
    $proxy_count{stderr}++;
    if (defined $dup{stderr}) {
      _open \*STDERR, ">&=" . fileno($dup{stderr});
       # _debug( "# restored proxy STDERR as " . (defined fileno STDERR ? fileno STDERR : 'undef' ) . "\n" );
    }
    else {
      _open \*STDERR, ">" . File::Spec->devnull;
       # _debug( "# proxied STDERR as " . (defined fileno STDERR ? fileno STDERR : 'undef' ) . "\n" );
      _open $dup{stderr} = IO::Handle->new, ">&=STDERR";
    }
    $proxies{stderr} = \*STDERR;
    binmode(STDERR, ':utf8') if $] >= 5.008; ## no critic
  }
  return %proxies;
}

sub _unproxy {
  my (%proxies) = @_;
  # _debug( "# unproxying: " . join(" ", keys %proxies) . "\n" );
  for my $p ( keys %proxies ) {
    $proxy_count{$p}--;
    # _debug( "# unproxied " . uc($p) . " ($proxy_count{$p} left)\n" );
    if ( ! $proxy_count{$p} ) {
      _close $proxies{$p};
      _close $dup{$p} unless $] < 5.008; # 5.6 will have already closed this as dup
      delete $dup{$p};
    }
  }
}

sub _copy_std {
  my %handles;
  for my $h ( qw/stdout stderr stdin/ ) {
    next if $h eq 'stdin' && ! $IS_WIN32; # WIN32 hangs on tee without STDIN copied
    my $redir = $h eq 'stdin' ? "<&" : ">&";
    _open $handles{$h} = IO::Handle->new(), $redir . uc($h); # ">&STDOUT" or "<&STDIN"
  }
  return \%handles;
}

# In some cases we open all (prior to forking) and in others we only open
# the output handles (setting up redirection)
sub _open_std {
  my ($handles) = @_;
  _open \*STDIN, "<&" . fileno $handles->{stdin} if defined $handles->{stdin};
  _open \*STDOUT, ">&" . fileno $handles->{stdout} if defined $handles->{stdout};
  _open \*STDERR, ">&" . fileno $handles->{stderr} if defined $handles->{stderr};
}

#--------------------------------------------------------------------------#
# private subs
#--------------------------------------------------------------------------#

sub _start_tee {
  my ($which, $stash) = @_; # $which is "stdout" or "stderr"
  # setup pipes
  $stash->{$_}{$which} = IO::Handle->new for qw/tee reader/;
  pipe $stash->{reader}{$which}, $stash->{tee}{$which};
  # _debug( "# pipe for $which\: " .  _name($stash->{tee}{$which}) . " " . fileno( $stash->{tee}{$which} ) . " => " . _name($stash->{reader}{$which}) . " " . fileno( $stash->{reader}{$which}) . "\n" );
  select((select($stash->{tee}{$which}), $|=1)[0]); # autoflush
  # setup desired redirection for parent and child
  $stash->{new}{$which} = $stash->{tee}{$which};
  $stash->{child}{$which} = {
    stdin   => $stash->{reader}{$which},
    stdout  => $stash->{old}{$which},
    stderr  => $stash->{capture}{$which},
  };
  # flag file is used to signal the child is ready
  $stash->{flag_files}{$which} = scalar tmpnam();
  # execute @cmd as a separate process
  if ( $IS_WIN32 ) {
    my $old_eval_err=$@;
    undef $@;

    eval "use Win32API::File qw/GetOsFHandle SetHandleInformation fileLastError HANDLE_FLAG_INHERIT INVALID_HANDLE_VALUE/ ";
    # _debug( "# Win32API::File loaded\n") unless $@;
    my $os_fhandle = GetOsFHandle( $stash->{tee}{$which} );
    # _debug( "# Couldn't get OS handle: " . fileLastError() . "\n") if ! defined $os_fhandle || $os_fhandle == INVALID_HANDLE_VALUE();
    my $result = SetHandleInformation( $os_fhandle, HANDLE_FLAG_INHERIT(), 0);
    # _debug( $result ? "# set no-inherit flag on $which tee\n" : ("# can't disable tee handle flag inherit: " . fileLastError() . "\n"));
    _open_std( $stash->{child}{$which} );
    $stash->{pid}{$which} = system(1, @cmd, $stash->{flag_files}{$which});
    # not restoring std here as it all gets redirected again shortly anyway
    $@=$old_eval_err;
  }
  else { # use fork
    _fork_exec( $which, $stash );
  }
}

sub _fork_exec {
  my ($which, $stash) = @_; # $which is "stdout" or "stderr"
  my $pid = fork;
  if ( not defined $pid ) {
    Carp::confess "Couldn't fork(): $!";
  }
  elsif ($pid == 0) { # child
    # _debug( "# in child process ...\n" );
    untie *STDIN; untie *STDOUT; untie *STDERR;
    _close $stash->{tee}{$which};
    # _debug( "# redirecting handles in child ...\n" );
    _open_std( $stash->{child}{$which} );
    # _debug( "# calling exec on command ...\n" );
    exec @cmd, $stash->{flag_files}{$which};
  }
  $stash->{pid}{$which} = $pid
}

my $have_usleep = eval "use Time::HiRes 'usleep'; 1";
sub _files_exist {
  return 1 if @_ == grep { -f } @_;
  Time::HiRes::usleep(1000) if $have_usleep;
  return 0;
}

sub _wait_for_tees {
  my ($stash) = @_;
  my $start = time;
  my @files = values %{$stash->{flag_files}};
  my $timeout = defined $ENV{PERL_CAPTURE_TINY_TIMEOUT}
              ? $ENV{PERL_CAPTURE_TINY_TIMEOUT} : $TIMEOUT;
  1 until _files_exist(@files) || ($timeout && (time - $start > $timeout));
  Carp::confess "Timed out waiting for subprocesses to start" if ! _files_exist(@files);
  unlink $_ for @files;
}

sub _kill_tees {
  my ($stash) = @_;
  if ( $IS_WIN32 ) {
    # _debug( "# closing handles\n");
    close($_) for values %{ $stash->{tee} };
    # _debug( "# waiting for subprocesses to finish\n");
    my $start = time;
    1 until wait == -1 || (time - $start > 30);
  }
  else {
    _close $_ for values %{ $stash->{tee} };
    waitpid $_, 0 for values %{ $stash->{pid} };
  }
}

sub _slurp {
  my ($name, $stash) = @_;
  my ($fh, $pos) = map { $stash->{$_}{$name} } qw/capture pos/;
  # _debug( "# slurping captured $name from " . fileno($fh) . " at pos $pos with layers: @{[PerlIO::get_layers($fh)]}\n");
  seek( $fh, $pos, 0 ) or die "Couldn't seek on capture handle for $name\n";
  my $text = do { local $/; scalar readline $fh };
  return defined($text) ? $text : "";
}

#--------------------------------------------------------------------------#
# _capture_tee() -- generic main sub for capturing or teeing
#--------------------------------------------------------------------------#

sub _capture_tee {
  # _debug( "# starting _capture_tee with (@_)...\n" );
  my ($do_stdout, $do_stderr, $do_merge, $do_tee, $code, @opts) = @_;
  my %do = ($do_stdout ? (stdout => 1) : (),  $do_stderr ? (stderr => 1) : ());
  Carp::confess("Custom capture options must be given as key/value pairs\n")
    unless @opts % 2 == 0;
  my $stash = { capture => { @opts } };
  for ( keys %{$stash->{capture}} ) {
    my $fh = $stash->{capture}{$_};
    Carp::confess "Custom handle for $_ must be seekable\n"
      unless ref($fh) eq 'GLOB' || (blessed($fh) && $fh->isa("IO::Seekable"));
  }
  # save existing filehandles and setup captures
  local *CT_ORIG_STDIN  = *STDIN ;
  local *CT_ORIG_STDOUT = *STDOUT;
  local *CT_ORIG_STDERR = *STDERR;
  # find initial layers
  my %layers = (
    stdin   => [PerlIO::get_layers(\*STDIN) ],
    stdout  => [PerlIO::get_layers(\*STDOUT, output => 1)],
    stderr  => [PerlIO::get_layers(\*STDERR, output => 1)],
  );
  # _debug( "# existing layers for $_\: @{$layers{$_}}\n" ) for qw/stdin stdout stderr/;
  # get layers from underlying glob of tied filehandles if we can
  # (this only works for things that work like Tie::StdHandle)
  $layers{stdout} = [PerlIO::get_layers(tied *STDOUT)]
    if tied(*STDOUT) && (reftype tied *STDOUT eq 'GLOB');
  $layers{stderr} = [PerlIO::get_layers(tied *STDERR)]
    if tied(*STDERR) && (reftype tied *STDERR eq 'GLOB');
  # _debug( "# tied object corrected layers for $_\: @{$layers{$_}}\n" ) for qw/stdin stdout stderr/;
  # bypass scalar filehandles and tied handles
  # localize scalar STDIN to get a proxy to pick up FD0, then restore later to CT_ORIG_STDIN
  my %localize;
  $localize{stdin}++,  local(*STDIN)
    if grep { $_ eq 'scalar' } @{$layers{stdin}};
  $localize{stdout}++, local(*STDOUT)
    if $do_stdout && grep { $_ eq 'scalar' } @{$layers{stdout}};
  $localize{stderr}++, local(*STDERR)
    if ($do_stderr || $do_merge) && grep { $_ eq 'scalar' } @{$layers{stderr}};
  $localize{stdin}++, local(*STDIN), _open( \*STDIN, "<&=0")
    if tied *STDIN && $] >= 5.008;
  $localize{stdout}++, local(*STDOUT), _open( \*STDOUT, ">&=1")
    if $do_stdout && tied *STDOUT && $] >= 5.008;
  $localize{stderr}++, local(*STDERR), _open( \*STDERR, ">&=2")
    if ($do_stderr || $do_merge) && tied *STDERR && $] >= 5.008;
  # _debug( "# localized $_\n" ) for keys %localize;
  # proxy any closed/localized handles so we don't use fds 0, 1 or 2
  my %proxy_std = _proxy_std();
  # _debug( "# proxy std: @{ [%proxy_std] }\n" );
  # update layers after any proxying
  $layers{stdout} = [PerlIO::get_layers(\*STDOUT, output => 1)] if $proxy_std{stdout};
  $layers{stderr} = [PerlIO::get_layers(\*STDERR, output => 1)] if $proxy_std{stderr};
  # _debug( "# post-proxy layers for $_\: @{$layers{$_}}\n" ) for qw/stdin stdout stderr/;
  # store old handles and setup handles for capture
  $stash->{old} = _copy_std();
  $stash->{new} = { %{$stash->{old}} }; # default to originals
  for ( keys %do ) {
    $stash->{new}{$_} = ($stash->{capture}{$_} ||= File::Temp->new);
    seek( $stash->{capture}{$_}, 0, 2 ) or die "Could not seek on capture handle for $_\n";
    $stash->{pos}{$_} = tell $stash->{capture}{$_};
    # _debug("# will capture $_ on " . fileno($stash->{capture}{$_})."\n" );
    _start_tee( $_ => $stash ) if $do_tee; # tees may change $stash->{new}
  }
  _wait_for_tees( $stash ) if $do_tee;
  # finalize redirection
  $stash->{new}{stderr} = $stash->{new}{stdout} if $do_merge;
  # _debug( "# redirecting in parent ...\n" );
  _open_std( $stash->{new} );
  # execute user provided code
  my ($exit_code, $inner_error, $outer_error, $orig_pid, @result);
  {
    $orig_pid = $$;
    local *STDIN = *CT_ORIG_STDIN if $localize{stdin}; # get original, not proxy STDIN
    # _debug( "# finalizing layers ...\n" );
    _relayer(\*STDOUT, $layers{stdout}) if $do_stdout;
    _relayer(\*STDERR, $layers{stderr}) if $do_stderr;
    # _debug( "# running code $code ...\n" );
    my $old_eval_err=$@;
    undef $@;
    eval { @result = $code->(); $inner_error = $@ };
    $exit_code = $?; # save this for later
    $outer_error = $@; # save this for later
    STDOUT->flush if $do_stdout;
    STDERR->flush if $do_stderr;
    $@ = $old_eval_err;
  }
  # restore prior filehandles and shut down tees
  # _debug( "# restoring filehandles ...\n" );
  _open_std( $stash->{old} );
  _close( $_ ) for values %{$stash->{old}}; # don't leak fds
  # shouldn't need relayering originals, but see rt.perl.org #114404
  _relayer(\*STDOUT, $layers{stdout}) if $do_stdout;
  _relayer(\*STDERR, $layers{stderr}) if $do_stderr;
  _unproxy( %proxy_std );
  # _debug( "# killing tee subprocesses ...\n" ) if $do_tee;
  _kill_tees( $stash ) if $do_tee;
  # return captured output, but shortcut in void context
  # unless we have to echo output to tied/scalar handles;
  my %got;
  if ( $orig_pid == $$ and ( defined wantarray or ($do_tee && keys %localize) ) ) {
    for ( keys %do ) {
      _relayer($stash->{capture}{$_}, $layers{$_});
      $got{$_} = _slurp($_, $stash);
      # _debug("# slurped " . length($got{$_}) . " bytes from $_\n");
    }
    print CT_ORIG_STDOUT $got{stdout}
      if $do_stdout && $do_tee && $localize{stdout};
    print CT_ORIG_STDERR $got{stderr}
      if $do_stderr && $do_tee && $localize{stderr};
  }
  $? = $exit_code;
  $@ = $inner_error if $inner_error;
  die $outer_error if $outer_error;
  # _debug( "# ending _capture_tee with (@_)...\n" );
  return unless defined wantarray;
  my @return;
  push @return, $got{stdout} if $do_stdout;
  push @return, $got{stderr} if $do_stderr && ! $do_merge;
  push @return, @result;
  return wantarray ? @return : $return[0];
}

1;

__END__